3553

Dithiolethiones are a class of potent cancer chemopreventive agents. The parent compound, 3H-1, 2-dithiole-3-thione (D3T) has been shown to act via an Nrf2-dependent mechanism, blocking cancer, in part, through the induction of carcinogen detoxication and antioxidant genes. Because oxidative and electrophilic stress has been implicated in numerous pathophysiological conditions including cancer, inflammation, cardiovascular disease and aging, exogenous antioxidants may exert profound cytoprotective effects. In order to identify the potentially broad influences of D3T on gene expression, hepatic tissue samples were analyzed using the Affymetrix RG-U34A&B chips. Male F344 rats, 4 per group, were treated by gavage with either vehicle (saturated sucrose) or D3T (0.3 mmol/kg) once every other day for 5 days. Tissues were harvested 24h after the third dose and snap frozen. For the RG-U34A chip, 3173 of the 8799 probe sets, present in at least 75% of either the control or D3T treated groups, were identified. The group comparison p-values (Mann-Whitney) were calculated for this set of genes, and all 3173 probe sets with their p-values and functional annotation (gene ontology) were analyzed simultaneously by a semi-supervised method of functional class scoring (http://microarray.genomecenter.columbia.edu/ermineJ/). The rational for including genes displaying subtle alteration in expression levels is based on the concept that such genes may be highly relevant to the biological function of the treatment when viewed in a large context of interacting genes, thus improving the identification of genes that act synergistically within a biological pathway. The top 10 classes of gene ontology influenced by D3T treatment included known classes such as glutathione and aldehyde metabolism, as well as several novel classes such as cholesterol synthesis (12/13 genes down-regulated) and ribosome constituents (68/85 genes up-regulated). A total of 395 probe sets from RG-U34A&B chips were selected for further analysis based on a p-value ≤ 0.05 and a fold change cutoff of 1.7. This set of 395 probe sets was used for pathway analysis with Ingenuity software (http://www.ingenuity.com). Nine statistically significant biological networks were identified. The canonical pathway and global biological function involved in the networks included increased bile acid synthesis and tyrosine metabolism, repressed immune response and IGF-1 signaling, as well as up-regulation of the genes involved in gluconeogenesis and down-regulation of the genes involved in glycolysis. Although the molecular mechanism for this similarity is unclear, this transcription profile of D3T obviously overlaps that of caloric restriction and the effects of statins, indicating broader effects than previously expected.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]